Air Compressor for Vehicles

Abstract

The present invention relates to an air compressor for a vehicle, which has improved internal cooling efficiency by ensuring a circulating flow of compressed air for internal cooling and allowing the compressed air to flow sufficiently. The air compressor includes: a housing; a compression unit disposed in the housing for introducing and compressing air from the outside; a motor unit disposed in the housing, including a rotor and a stator, and driving the compression unit to rotate according to the rotation of the rotor; a bearing unit for supporting the rotor to be rotatable; a cooling circulation flow passage formed in the housing for moving some of the air compressed in the compression unit in the axial direction and circulating the air to the compression unit; and a bypass flow passage for receiving some of the air passing through the cooling circulation flow passage and bypassing a partial area of the bearing unit and converging with the cooling circulation flow passage.

Description

Technical Field

[0001] The present invention relates to a compressor, and more particularly, to an air compressor for a vehicle, in which the cooling efficiency is improved by increasing the circulation flow rate of cooling air. Background Art

[0002] Generally, a fuel cell vehicle is a vehicle in which hydrogen and oxygen are supplied to a humidifier so that electric energy generated by an electrochemical reaction, which is the reverse reaction of electrolysis of water, is supplied as a driving force of the vehicle. A general fuel cell vehicle is disclosed in Korean Patent Registration No. 0962903.

[0003] Generally, a fuel cell vehicle for riding includes a 100 kW fuel cell stack. Here, when the fuel cell stack is operated while being pressurized, air supplied to the fuel cell stack is supplied at a high pressure of 1 bar to 4 bar. For this purpose, an air compressor having a speed of 100,000 to 200,000 revolutions per minute (RPM) must be used.

[0004] A fuel cell vehicle generally includes a fuel cell stack configured to generate electricity, a humidifier configured to increase the humidity of air supplied to the fuel cell stack, a fuel supply unit configured to supply hydrogen to the fuel cell stack, an air supply unit configured to supply air including oxygen to the fuel cell stack, a cooling module configured to cool the fuel cell stack, and the like.

[0005] The air supply unit includes: an air filter configured to filter foreign substances contained in air; an air compressor configured to compress and supply the air filtered by the air filter; a cooling device configured to cool high-temperature pressurized air; a humidifier configured to increase the humidity of the air; and a valve configured to adjust the flow rate.

[0006] The air compressor compresses air inhaled from the outside using a compressor impeller and then sends the compressed air to the fuel cell stack.

[0007] Here, the compressor impeller is connected to a rotating shaft that receives power from a driving unit, and the driving unit generally drives the rotating shaft through electromagnetic induction of a stator and a rotor.

[0008] Here, in the air compressor, heat loss caused by air resistance at an air bearing occurs due to the high-speed rotation of the rotor, and thus it is necessary to cool a motor and a bearing, which are main heat sources. Accordingly, a structure is provided in which some of the compressed air generated by the impeller of the air compressor is used to cool the motor and the bearing for rotating the impeller, and then the air is introduced into the inlet side of the impeller through an inner hole of the rotating shaft of the motor.

[0009] Correspondingly, Korean Patent Registration No. 1810430 discloses an air compressor and a fuel cell vehicle that circulate internal air flow at the end of a motor shaft. Herein, the air compressor includes: a drive housing in which a rotor and a stator are constructed; a motor shaft in which an air discharge hole is formed through the drive housing; an air bearing that is coupled to the rear end of the housing of the drive housing to support the rear end of the shaft of the motor shaft; and a motor cooling channel in which cooling air collected in an outer chamber of the motor via an internal space of the drive housing is extracted from compressed air formed by an impeller in an impeller chamber, and the cooling air is sucked through the air discharge hole and discharged from the rear end of the shaft to the front end of the shaft.

[0010] However, the above-described conventional air compressor has a problem in that when compressed air passes through a narrow space near an airfoil bearing, the flow rate of the compressed air decreases and its air flow is delayed, so the self-cooling efficiency using the compressed air is reduced. Summary of the Invention

[0011] Technical Problem

[0012] The present invention aims to provide an air compressor for a vehicle that ensures the circulating flow rate of cooling air and promotes the flow of cooling air to improve cooling efficiency.

[0013] Aspects of the present invention are not limited to the above aspects, and those skilled in the art will understand other unstated aspects of the present invention from the following disclosure.

[0014] Technical Solution

[0015] One aspect of the present invention provides an air compressor for a vehicle. The air compressor includes: a compression unit disposed on one side of a rotor to generate compressed air by compressing air flowing therein; a bearing unit configured to support the rotor in a front-rear direction; a cooling circulation flow channel configured to allow the compressed air discharged from the compression unit to flow in the bearing unit to cool the bearing unit; and a bypass flow channel configured to allow some of the compressed air to bypass at least a part of the bearing unit.

[0016] The cooling circulation flow channel and the bypass flow channel may bifurcate in front of the bearing unit or at a point where the bearing unit is provided and may converge behind the bearing unit.

[0017] Some of the converged compressed air may be discharged outward.

[0018] The air compressor may further include a housing configured to accommodate the compression section, the bearing section, the cooling circulation flow passage, and the bypass flow passage.

[0019] The housing may include a rear cover disposed behind the rotor.

[0020] The rear cover may be made of plastic material.

[0021] The rear cover may include a discharge hole formed to extend toward the rear portion of the rotor, and the compressed air may be discharged through the discharge hole.

[0022] The rotor may include a rotating shaft coupled to the compression section, a rotor portion coupled to the outer peripheral surface of the rotating shaft, and a rotor disk formed at the rear side of the rotor portion.

[0023] The bearing section may include a front air foil bearing and a rear air foil bearing that respectively support the front surface and the rear surface of the rotor disk.

[0024] The cooling circulation flow passage and the bypass flow passage may branch between the front air foil bearing and the rear air foil bearing.

[0025] The cooling circulation flow passage may include: a cooling flow passage disposed outside the rotor to move a part of the air compressed by the compression section from the front to the rear; and a circulation flow passage disposed inside the rotor to circulate and supply the air moved from the cooling flow passage to the compression section.

[0026] The cooling circulation flow passage may further include a chamber disposed between the cooling flow passage and the circulation flow passage.

[0027] The bypass flow passage may converge with the chamber.

[0028] The width of the chamber may be greater than the width of the cooling flow passage or the bypass flow passage.

[0029] Rotating air rotating in one direction may be formed in the chamber, and the rotating air rotates in a direction from the outlet of the bypass flow passage to the inlet of the circulation flow passage.

[0030] Due to the flow of the rotating air, the compressed air flowing into the chamber from the bypass flow passage may be transferred to the rear portion of the chamber.

[0031] The bypass flow passage may be closer to the rotor in a direction toward the chamber.

[0032] The chamber may be provided inside the rear cover.

[0033] Advantageous Effects

[0034] According to the present invention, in an air compressor for a vehicle, since a bypass flow passage bypassing the air foil bearing is additionally installed, the circulating flow velocity of the compressed air for internal cooling can be ensured, and the circulation of the internal compressed air can be promoted to improve the cooling efficiency of the cooling air.

[0035] According to the present invention, in an air compressor for a vehicle, since the rotating air is formed in the air inside the chamber in a direction consistent with the conveying direction, the phenomenon of static air formation at the position where various flow passages meet can be prevented, and the rotating air can be used to cause heat exchange with the cooling air near the bearing to improve the cooling efficiency of the cooling air. Description of the Drawings

[0036] Figure 1 is a cross-sectional view of an air compressor for a vehicle according to an embodiment of the present invention.

[0037] Figure 2 is a cross-sectional view showing a cooling circulation flow passage according to an embodiment of the present invention.

[0038] Figure 3 is a block diagram showing a passage of compressed air of an air compressor according to an embodiment of the present invention.

[0039] Figure 4 is a view showing the heat distribution of an air compressor according to an embodiment of the present invention.

[0040] Figure 5 is a view showing the heat distribution of the air inside an air compressor according to an embodiment of the present invention.

[0041] Figure 6 is an enlarged cross-sectional view showing a connecting portion of a second cooling flow passage, a bypass flow passage, a chamber, and a circulation flow passage of an air compressor according to an embodiment of the present invention.

[0042] Figure 7 is a view showing the air flow at a connecting portion of a second cooling flow passage, a bypass flow passage, a chamber, and a circulation flow passage of an air compressor according to an embodiment of the present invention. Detailed Description of the Invention

[0043] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings.

[0044] However, the technical concept of the present invention is not limited to the embodiments described below and can be implemented in various different forms. Without departing from the technical concept of the present invention, one or more components of the embodiments can be selectively combined with or replaced by each other.

[0045] In addition, unless otherwise specifically defined, the terms (including technical or scientific terms) used herein can have the same meaning as commonly understood by those of ordinary skill in the art. Commonly used terms can be interpreted in consideration of the context of the related art, such as terms defined in a dictionary.

[0046] In addition, the terms used herein are intended to explain the embodiments and do not limit the present invention.

[0047] Throughout the specification, the singular forms also include the plural forms unless the context clearly indicates otherwise. When describing at least one (or one or more) of A, B, and C, this can include one or more of all combinations of A, B, and C.

[0048] In addition, when describing components of embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. can be used.

[0049] These terms are only used to distinguish one element from another, and the nature, order, sequence, etc. of the corresponding elements are not limited by these terms.

[0050] Moreover, when stating that one element is "connected", "coupled", or "joined" to another element, the element can not only be directly connected, coupled, or joined to another element, but can also be connected, coupled, or joined to another element through another intermediate element.

[0051] Moreover, when stating that one element is formed or disposed "above (over) or below (under)" another element, the two elements can not only be in direct contact with each other, but also one or more other elements can be formed or disposed between the two elements. In addition, "above (over) or below (under)" can include not only the upward direction based on one element, but also the downward direction.

[0052] Hereinafter, refer to Figures 1 to 5 Describe an air compressor for a vehicle according to an embodiment of the present invention.

[0053] Figure 1 is a cross-sectional view of an air compressor according to an embodiment of the present invention, Figure 2 is a cross-sectional view showing a cooling cycle flow passage according to an embodiment of the present invention, Figure 3 is a block diagram showing a passage of compressed air of an air compressor according to an embodiment of the present invention, Figure 4is a view showing the thermal distribution of an air compressor according to an embodiment of the present invention, and Figure 5 is a view showing the thermal distribution of air within an air compressor according to an embodiment of the present invention.

[0054] Referring to Figure 1 and Figure 2 , the air compressor includes a housing 100, a compression unit 200, a drive unit 300, a bearing unit 400, a cooling circulation flow path 500, and a bypass flow path 600.

[0055] The housing 100 forms the exterior. The housing 100 houses the compression unit 200, the drive unit 300, the bearing unit 400, the cooling circulation flow path 500, and the bypass flow path 600 within its internal space. Here, the housing 100 may include an impeller housing 110, a drive housing 120, and a rear cover 130.

[0056] The impeller housing 110 may include an inlet 111 and an outlet 112. Additionally, the compression unit 200 is disposed within the internal space of the impeller housing 110. Here, the air flowing in through the inlet 111 is compressed by the compression unit 200 and discharged outward through the outlet 112. Here, some of the compressed air is supplied to the cooling circulation flow path 500 described below.

[0057] The drive housing 120 is connected to the rear end of the impeller housing 110. Here, backward is the direction toward the drive unit 300, and forward is the direction opposite to the rear based on the compression unit 200. Here, the drive unit 300 is disposed within the internal space of the drive housing 120. Additionally, the cooling circulation flow path 500 is formed within the drive housing 120.

[0058] The rear cover 130 is connected to the rear end of the drive housing 120. Here, a chamber 530 described below may be disposed within the internal space of the rear cover 130. The rear cover 130 may be made of a plastic material.

[0059] Here, the rear cover 130 may include a discharge hole (not shown) that opens toward the rear side of the air compressor.

[0060] The compression unit 200 is disposed within the internal space of the impeller housing 110 and compresses the air flowing in through the inlet 111. The compression unit 200 may include a blower 210 and an impeller 220.

[0061] The blower 210 is connected to the inlet 111 and has a shape with a gradually decreasing cross-section to compress the air flowing therein.

[0062] The impeller 220 may be disposed between the inlet 111 and the blower 210. Here, the impeller 220 may convey the air that has flowed in through the inlet 111 toward the blower 210.

[0063] That is to say, the air that has flowed in through the inlet 111 can be conveyed to the blower 210 through the impeller 220 and compressed when passing through the blower 210 with a gradually decreasing cross-section to generate compressed air. Here, some of the compressed air flows through the cooling circulation flow channel 500. Here, the compressed air can perform the function of cooling the inside of the air compressor.

[0064] The driving unit 300 is disposed in the inner space of the driving housing 120 and provides driving force for the compression unit 200. Here, the driving unit 300 may include a rotor 310 and a stator 320.

[0065] One side of the rotor 310 is connected to the compression unit 200 and rotates the compression unit 200 while rotating. Here, the rotor 310 may include a rotating shaft 311, a rotor portion 312, and a rotor disk 313.

[0066] The rotating shaft 311 is coupled to the impeller 230 and drives the impeller 230 to rotate.

[0067] The rotor portion 312 is coupled to the outer peripheral surface of the rotating shaft 311. Here, when external power is supplied, the rotor portion 312 generates torque due to the electromagnetic interaction with the stator 320. Here, referring to Figure 4 and Figure 5 , heat is concentrated on the rotor disk 313 and the portion where the rotor portion 312 and the stator 320 overlap. Moreover, the temperature of the air passing between the rotor portion 312 and the stator 320 increases.

[0068] The rotor disk 313 is connected to one side of the rotor portion 312. The radial length of the rotor disk 313 may be greater than the radial length of the rotor portion 312. Here, heat is concentrated on both sides of the rotor disk 313 and the air in contact with both sides of the rotor disk 313.

[0069] The stator 320 is disposed outside the rotor 310 and fixedly mounted on the inner peripheral surface of the driving housing 120. Here, outward is the direction toward the housing 100 based on the rotating shaft 311, and inward is the direction opposite to the outward direction.

[0070] Meanwhile, although not shown in the figures, the driving unit may be configured as a clutch (not shown) and may receive the driving force of the vehicle engine to operate. The driving unit may include a pulley (not shown), a disc assembly (not shown), a coil assembly (not shown), etc. Here, the pulley is connected to the vehicle engine via a transmission belt (not shown), and the transmission belt may be mounted on the outer circumferential surface of the pulley and may transmit the power of the vehicle engine to the pulley. Similarly, the disc assembly may be coupled to a drive shaft (not shown) and may transmit the power of the vehicle engine from the pulley to the drive shaft. Here, the drive shaft serves as the rotating shaft 311 and is coupled to the impeller 340 to drive the impeller 340 to rotate.

[0071] The bearing unit 400 rotatably supports the rotor 310. Here, the bearing unit 400 may include front and rear journal bearings 410 and 420 and front and rear aerodynamic bearings 430 and 440.

[0072] The front and rear journal bearings 410 and 420 are disposed at both ends of the outer circumferential surface of the rotor portion 312 and support the rotor portion 312 to rotate smoothly within the drive housing 120.

[0073] The front and rear aerodynamic bearings 430 and 440 are disposed on the front and rear surfaces of the rotor disc 313 and support the rotation of the rotor disc 313 in the axial direction. Here, referring to Figure 2 , heat is concentrated on the portions of the rotor disc 313 that come into contact with the front and rear aerodynamic bearings 430 and 440.

[0074] Referring to Figure 2 , the cooling circulation flow channel 500 allows some of the air compressed by the compression unit 200 to move in the axial direction and then circulate through the compression unit 200. Here, the cooling circulation flow channel 500 may include a cooling flow channel 510 and a circulation flow channel 520.

[0075] The cooling flow channel 510 may be disposed outside the rotor 310. Here, the cooling flow channel 510 may be formed by the space between the drive housing 120 and the driving unit 300. The cooling flow channel 510 may move some of the air compressed by the compression unit 200 from the front to the rear.

[0076] Figure 6 is an enlarged cross-sectional view showing the connection portions of the second cooling flow channel, bypass flow channel, chamber, and circulation flow channel of an air compressor according to an embodiment of the present invention, Figure 7 is a view showing the air flow at the connection portions of the second cooling flow channel, bypass flow channel, chamber, and circulation flow channel of an air compressor according to an embodiment of the present invention.

[0077] Referring to Figure 2 and Figure 6, the cooling flow channel 510 may include a first cooling flow channel 511 and a second cooling flow channel 512.

[0078] The first cooling flow channel 511 surrounds the outer surface of the rotor portion 312 and the front and rear journal bearings 410 and 420, and allows compressed air to pass through to cool the heat generated at the rotor portion 312, the front and rear journal bearings 410 and 420, and the stator 320.

[0079] In addition, the second cooling flow channel 512 surrounds the outer surface of the rotor disk 313 and the outer surfaces of the front and rear aerodynamic bearings 430 and 440, and allows compressed air to pass through to cool the heat generated at the rotor disk 313 and the front and rear aerodynamic bearings 430 and 440.

[0080] Referring to Figure 6 and Figure 7 , the second cooling flow channel 512 may include a first region 5121, a second region 5122, and a third region 5123.

[0081] The first region 5121 surrounds the front surface of the rotor disk 313 and the front aerodynamic bearing 430 and cools the heat generated on the front surface of the rotor disk 313 and the front aerodynamic bearing 430.

[0082] The second region 5122 surrounds the side surface of the rotor disk 313 and cools the heat generated on the side surface of the rotor disk 313.

[0083] The third region 5123 surrounds the rear surface of the rotor disk 313 and the rear aerodynamic bearing 440 and cools the heat generated on the rear surface of the rotor disk 313 and the rear aerodynamic bearing 440.

[0084] In addition, the cooling flow channel 510 may further include a third cooling flow channel 513 configured to bypass the rear journal bearing 420 and connect the first cooling flow channel 511 to the second cooling flow channel 512.

[0085] The circulating flow channel 520 may be provided inside the rotor 310. The circulating flow channel 520 may be formed by the hollow portion of the rotating shaft 311. The circulating flow channel 520 may be connected to the rear end of the cooling flow channel 510 and may receive and circulate the air moving from the cooling flow channel 510 to supply the air to the inlet 111.

[0086] In addition, the cooling circulation flow channel 500 may further include a chamber 530 connected between the cooling flow channel 510 and the circulating flow channel 520. The chamber 530 transfers the air moving from the cooling flow channel 510 to the circulating flow channel 520. Here, air turbulence may occur in the chamber 530.

[0087] On the other hand, the compressed air that converges from the cooling flow passage 510 and the bypass flow passage 600 can be discharged backward from the air compressor through the discharge hole of the rear cover 130.

[0088] The bypass flow passage 600 receives some of the air passing through the cooling circulation flow passage 500, allows the air to bypass a part of the bearing portion 400, and converges with the cooling circulation flow passage 500.

[0089] The cooling circulation flow passage 500 and the bypass flow passage 600 can branch off in front of the bearing portion 400 or at the point where the bearing portion 400 is provided. Here, the cooling circulation flow passage 500 and the bypass flow passage 600 can converge with each other behind the bearing portion 400.

[0090] Here, the cooling circulation flow passage 500 and the bypass flow passage 600 can branch off between the front aerostatic bearing 430 and the rear aerostatic bearing 440.

[0091] More specifically, the bypass flow passage 600 can branch off from the second region 5122. Here, referring to Figure 5 , the air passing through the bypass flow passage 600 can bypass the rear aerostatic bearing 440 and converge with the cooling circulation flow passage 500.

[0092] The bypass flow passage 600 can increase the circulation flow rate of the cooling air in the compressor, and alleviate the phenomenon of air flow delay in the portion near the aerostatic bearing, so as to promote the circulation of the compressed air therein and increase the internal cooling efficiency.

[0093] Moreover, the bypass flow passage 600 can converge with the chamber 530. Here, the bypass flow passage 600 can be closer to the rotor 310 in the direction toward the chamber 530.

[0094] Here, the connection point of the chamber 530 and the bypass flow passage 600 can be farther from the rotor 310 than the connection point of the chamber 530 and the cooling flow passage 510. In addition, the width of the chamber 530 can be greater than the width of the cooling flow passage 510 or the bypass flow passage 600.

[0095] Here, referring to Figure 7, the air flowing into the chamber 530 from the cooling flow channel 510 collides with the inner wall of the rear cover 130 and moves near the corner. In addition, the air can move along the inner wall of the rear cover 130 toward the outlet of the cooling flow channel 510 and the outlet of the bypass flow channel 600. Therefore, in the chamber 530, rotational air rotating in one direction can be formed. Here, the rotational air rotates to sequentially pass through the outlet of the bypass flow channel 600, the outlet of the cooling flow channel 510, and the inlet of the circulation flow channel 520. Here, the air that has flowed into the chamber 530 from the bypass flow channel 600 is conveyed to the rear of the chamber 530 along the rotational air flow, so the speed of flowing into the circulation flow channel 520 can be increased.

[0096] With this configuration, the air rotating in the chamber 530 can promote the air flow at the connection points of the cooling flow channel 510, the circulation flow channel 520, and the bypass flow channel 600, and increase the heat exchange efficiency of the compressed air near the bearing, so as to improve the cooling efficiency of the air compressor.

[0097] Although the exemplary embodiments of the present invention have been described above, those skilled in the art can understand that various modifications and changes can be made to the present invention without departing from the concepts and scopes of the present invention disclosed in the appended claims.

[0098] <Description of Reference Numerals>

[0099] 100: housing, 110: impeller housing, 120: drive housing, 130: rear cover, 200: compression part, 210: blower, 220: impeller, 300: drive part, 310: rotor, 311: rotating shaft, 312: rotor part, 313: rotor disc, 320: stator, 400: bearing part, 410: front journal bearing, 420: rear journal bearing, 430: front air foil bearing, 440: rear air foil bearing, 500: cooling circulation flow channel, 510: cooling flow channel, 511: first cooling flow channel, 512: second cooling flow channel,

[0100] 513: third cooling flow channel, 520: circulation flow channel,

[0101] 530: chamber, 600: bypass flow channel.

Claims

1. An air compressor for a vehicle, the air compressor comprising: A compression part disposed on one side of a rotor to generate compressed air by compressing air flowing therein; A bearing part configured to support the rotor in a front-rear direction; A cooling circulation flow passage configured to allow the compressed air discharged from the compression part to flow in the bearing part to cool the bearing part; A bypass flow passage configured to allow the compressed air to bypass at least a part of the bearing part; And A rear cover disposed behind the rotor, The rotor includes: A rotating shaft coupled to the compression part; A rotor part coupled to an outer circumferential surface of the rotating shaft; and A rotor disk formed at a rear side of the rotor part, The bearing part includes a front air foil bearing and a rear air foil bearing that respectively support a front surface and a rear surface of the rotor disk, The cooling circulation flow passage and the bypass flow passage branch between the front air foil bearing and the rear air foil bearing, The air passing through the bypass flow passage bypasses the rear air foil bearing and merges with the cooling circulation flow passage.

2. The air compressor according to claim 1, wherein, Some of the merged compressed air is discharged outward.

3. The air compressor according to claim 1, wherein, At least some of the merged compressed air is supplied to the compression part through the cooling circulation flow passage.

4. The air compressor according to claim 1, wherein, The air compressor further includes a housing configured to accommodate the compression part, the bearing part, the cooling circulation flow passage, and the bypass flow passage.

5. The air compressor according to claim 1, wherein, The rear cover is made of plastic material.

6. The air compressor according to claim 1, wherein, The rear cover includes at least one discharge hole formed to extend rearward, and Wherein, the compressed air is discharged through the discharge hole.

7. The air compressor according to claim 1, wherein The cooling circulation flow passage includes: A cooling flow passage disposed outside the rotor to move some of the air compressed by the compression part from the front to the rear; and A circulation flow passage disposed inside the rotor to circulate and supply the air moved from the cooling flow passage to the compression part.

8. The air compressor according to claim 7, wherein, The cooling circulation flow passage further includes a chamber disposed between the cooling flow passage and the circulation flow passage.

9. The air compressor according to claim 8, wherein, The bypass flow passage merges with the chamber.

10. The air compressor according to claim 9, wherein, The width of the chamber is greater than the width of the cooling flow passage or the bypass flow passage.

11. The air compressor according to claim 10, wherein, Rotating air rotating in one direction is formed in the chamber, and at the same time, the rotating air rotates in a direction from an outlet of the bypass flow passage to an inlet of the circulation flow passage.

12. The air compressor according to claim 11, wherein, Due to the flow of the rotating air, the compressed air flowing into the chamber from the bypass flow passage is transferred to the rear of the chamber.

13. The air compressor according to claim 12, wherein, The bypass flow passage is closer to the rotor in a direction toward the chamber.

14. The air compressor according to claim 13, wherein, The chamber is disposed inside the rear cover.

Images